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Misfire that JUST WON'T DIE!
https://slantsix.org/forum/viewtopic.php?t=68783		 Page 2 of 3
Author:  SlantSixDan [ Mon Oct 12, 2026 11:23 am ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
goal is to hit oreilly's for a new one right as they open and, with any luck, have the thing back together by the time I leave for work.
You're reminding me of one of my teenaged follies; search this page for pointy little head.
Author:  Plymouth_Ruster [ Mon Oct 12, 2026 1:35 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:

You're reminding me of one of my teenaged follies; search this page for pointy little head.
Ha! Luckily I've now had enough similar experiences that the daily gets first repair priority, and the truck gets second. The Scamp is a distant third but the other two have been trouble-free, despite one having a big badge on the front that says "JEEP."
Author:  Plymouth_Ruster [ Thu Oct 15, 2026 5:33 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Alright, I've got it narrowed down now; anything more than 16 degrees of timing makes it misfire. 16 is the most it gets out of the mechanical advance plus the five degrees of base, or base plus vacuum advance. It'll go past idle with the vac advance hooked up, but only until the mechanical starts to kick in. Ignition is strong and steady according to the light. I've taken the carb apart twice today, nothing wrong with it. All ports clear, all check balls in, no vacuum leaks as far as I can tell. No leaks at the manifold; used a Remflex gasket. PCV is hooked up, brake booster doesn't leak, I'm running out of things to check here. Before anyone asks, no, the needle and seat don't leak, and the floats aren't sunk. Changing float height had the single effect of making the accelerator pump not work as well.

I found another post on this forum, from years ago, of someone with the exact same issue - of course, they never explained how or if they ever solved it.
Author:  SlantSixDan [ Thu Oct 15, 2026 6:29 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
I'm running out of things to check here.
Naw y'ain't, yet. »cough«StillThinkItCouldBeYerCamTiming»cough«
Author:  Plymouth_Ruster [ Thu Oct 15, 2026 8:45 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
Quote:
I'm running out of things to check here.
Naw y'ain't, yet. »cough«StillThinkItCouldBeYerCamTiming»cough«
This thing has had about 50k on it since its last rebuild, sometime in the 90s. The timing set is an old Cloyes kit, so not exactly bad quality, and I saw a video of this thing running and running well. Previous owner had zero issues with it. I'll check valve timing from the top end, but I'm not tearing the timing cover off again unless I can find a good reason.
Author:  Plymouth_Ruster [ Thu Oct 15, 2026 9:37 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Alright, here we go, definitive proof that the cam timing is just fine. Stuck a dial indicator on the #1 intake rocker with the rocker depressed onto the pushrod via the spring in the dial indicator. As I understand it, most if not all stock slant six cams should have the intake opening 10 degrees BTDC. So I turned the crank until the dial indicator moved, stopped it, annnnd...

Image

Eleven degrees BTDC! Or twelve. Take your pick, doesn't really matter as two degrees difference shouldn't matter either way, let alone cause the issues I've been having.

Edit: Just went out and checked for reversed wires in the pickup harness and, as expected, nothing wrong with them.
Author:  SlantSixDan [ Fri Oct 16, 2026 1:22 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Okeh, next question: where are the rest of the hoses that are meant to be connected to your charcoal can?
Author:  Plymouth_Ruster [ Fri Oct 16, 2026 3:12 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
Okeh, next question: where are the rest of the hoses that are meant to be connected to your charcoal can?
Rotted off or deleted. Tank has a vented cap and all the ports on the carb that aren't needed are plugged off. I think the one that's left is connected to the tank vent.
Author:  Rick Covalt [ Fri Oct 16, 2026 5:10 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
No leaks at the manifold; used a Remflex gasket.
Have you sprayed carb claner around the manifold to head junction? The Remflex can seal well, but they can tear/split also. I had a bad air leak on start up of a new engine one time and it would barely start at all. It was on the underside of the intake against the head.
Author:  Plymouth_Ruster [ Fri Oct 16, 2026 5:49 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
Quote:
No leaks at the manifold; used a Remflex gasket.
Have you sprayed carb claner around the manifold to head junction? The Remflex can seal well, but they can tear/split also. I had a bad air leak on start up of a new engine one time and it would barely start at all. It was on the underside of the intake against the head.
Did that, yeah. Also used a mirror to check the underside of the intake for cracks; found none. Actually had to get the gasket replaced twice on the seller's dime because they kept packing the thing in a cardboard sleeve with too little cushioning, and the slant 6 gasket is both heavy enough and weak enough to crush itself sideways if it slides around in the packaging.
Author:  SlantSixDan [ Fri Oct 16, 2026 10:21 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Quote:
Quote:
]
Okeh, next question: where are the rest of the hoses that are meant to be connected to your charcoal can?
Rotted off or deleted. Tank has a vented cap and all the ports on the carb that aren't needed are plugged off. I think the one that's left is connected to the tank vent.
Ugh. Fix this bodged-up mess correctly when you get a chance and a bunch of stuff will get better. Read this for info. Be sure the hose routing to and from the charcoal can follows Chrysler's directions as described here and pictured here.

As to your more immediate problem of low power output and crummy running: any ping/spark knock? And what's the car's exhaust system like? Old, new? Stock/other?
Author:  Rick Covalt [ Sat Oct 17, 2026 5:15 am ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Maybe a video of this running would help? You do know the last thing you check will be the first thing that was wrong! :D Hang in there you will figure it out.
Author:  Plymouth_Ruster [ Sat Oct 17, 2026 9:34 am ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Ugh. Fix this bodged-up mess correctly when you get a chance and a bunch of stuff will get better. Read this for info. Be sure the hose routing to and from the charcoal can follows Chrysler's directions as described here and pictured here.

As to your more immediate problem of low power output and crummy running: any ping/spark knock? And what's the car's exhaust system like? Old, new? Stock/other?
[/quote]

I don't hear any pinging, but it's kinda hard to hear anyrhing at all over the fan noise and exhaust. The exhaust is a stock manifold followed by a 2.25" pipe I fabricated with a stock exhaust flange i welded to it. It's not restrictive, if that's what you're thinking.

I'll get a video later today.
Author:  Plymouth_Ruster [ Sat Oct 17, 2026 2:29 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Here we go, meant to do this a lot earlier but completely forgot.

https://youtu.be/tQLAP2ZY8dc?si=wJeT8cxC8GrUWMP2

No idea how to embed youtube videos on this forum. Ignore the knock, that's a loose rocker.
Author:  SlantSixDan [ Sun Oct 18, 2026 2:54 pm ]
Post subject:  Re: Misfire that JUST WON'T DIE!
Please try again with the microphone out of the exhaust blast. The "wind" noise is masking any misfires we're supposed to be hearing. Put the camera off to the side of the tailspout, not in line with it.

Then also bring the camera to the front of the car and let us see/hear what the engine looks and sounds like up there.

In both places, try to demonstrate the misfire.
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